Electrochemical synthesis of polyaniline–polypyrrole composite coatings on carbon fibres in aqueous toluene sulphonate solution

Polyaniline and polypyrrole were codeposited electrochemically on carbon fibres under potentiostatic conditions. Electropolymerisation was carried out by varying the applied potential and the feed ratio of monomers. The progress of electropolymerisation was monitored by weight gain analysis and infrared spectroscopy. The thermal stability of the coatings was determined by using thermogravimetric analysis and differential scanning calorimetry. Characteristic behaviour of polyaniline and polypyrrole can be deduced from the weight gain plots. Formation of polyaniline–polypyrrole composite coatings was further confirmed by the presence of characteristic peaks for polyaniline and polypyrrole in the infrared spectra. Thermal analysis also revealed the behaviour of the composite. Composite coatings composed of polyaniline and polypyrrole were formed at applied potentials of <1·0 V. Polypyrrole is preferentially formed at 1·5 V. Scanning electron micrographs were also used to illustrate the composite behaviour.